(1) Field of the Invention
The present invention relates to caliper type brakes for bicycles and, more particularly, to a caliper type brake in which a spring adjusting device is inserted in supporting portion for a return spring used in a brake mechanism, thereby the spring force is equalized in both sides of the return spring and adjustment for preventing the unbalanced braking ability can be readily effected.
(2) Description of the Prior Art
A conventional caliper type brake for bicycles is constituted as illustrated in FIGS. 1 and 2. There is shown a brake comprising a left block 1 and a right block 2 which are connected together by a through bolt 3 with washers 4 and 5 and are fixed at a definite position by a nut 7. Numeral 8 designates a locknut. Referring to FIG. 3, the through bolt 3 consists of bolt portions 9, 9' and a collar 10. The left block 1 and the right block 2 are attached to the bolt portion 9. The through bolt 3 is attached to a bicycle frame (not shown) at the bolt portion 9' through washers 11, 11' and is fixed by a washer 12 and a nut 13. The collar 10 is provided with a groove 15 to which the center horizontal portion of a return spring 14 is fitted and supported. Both ends of the return spring 14 are attached respectively to the inside of spring supports 1', 2' connected to the left block 1 and the right block 2 by means of spot welding, so that both blocks 1, 2 are stretched outwards. Ends of the left block 1 and the right block 2 are respectively provided with brake rubbers 16, 16'. A wire clamping screw 17 is attached to the other end of the left block 1; an adjusting screw 19 is attached to the other end of the right block 2 through a setscrew 18. An outer wire 20 of a brake operating Bowden cable is supported to the upper end of the adjusting screw 19, and an inner wire 21 thereof is fixed by inserting the lower end to the wire clamping screw 17.
After the caliper type brake constituted as above is attached to a bicycle frame, the brake rubbers 16, 16' are brought into contact with the side surface of a rim 28 and the inner wire 21 is fixed by the wire clamping screw 17, and then the clearance between the rim and the brake rubber is finely adjusted by the adjusting screw 19. Although the clearance between the rim and the brake rubber must be balanced in right and left directions, working tolerance in the size and tension of the return spring 14 may cause to unequal spring force in right and left directions and also to unbalanced braking ability. In prior art, the adjustment of the clearance between the brake rubber and the rim had to be effected by very troublesome process such that the return spring is changed or that the through bolt 3 is released from the fixing state to the frame and rotated for the clearance adjustment in right and left directions.